JP2021189280A - Image forming apparatus - Google Patents

Abstract

To obtain stable transfer performance without providing a large arrangement space for a high-voltage substrate on the inside of an intermediate transfer belt.SOLUTION: An image forming apparatus comprises: a first unit that has an intermediate transfer belt (31) and a first roller (32) that is arranged in contact with an inner surface of the intermediate transfer belt, and can be drawn out from an apparatus main body of the image forming apparatus; a second unit that has a second roller (41) that is arranged to be contactable with an outer surface of the intermediate transfer belt and a high-voltage substrate that applies voltage to the first roller, and can be drawn out from the apparatus main body; and an electric contact unit configured such that in a state in which the second unit is mounted at a predetermined mounting position of the apparatus main body, the high-voltage substrate and the first roller are electrically connected with each other, and in a state in which the second unit is drawn out from the mounting position, the connection between the high-voltage substrate and the first roller is released.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus that forms an image on a recording material.

In the image forming apparatus of the intermediate transfer method, the toner image formed on the photoconductor is first transferred to the intermediate transfer belt, and then the toner image is secondarily transferred from the intermediate transfer belt to the recording material in the secondary transfer unit. The secondary transfer portion is a nip portion formed between a secondary transfer roller in contact with the outer surface of the intermediate transfer belt and an opposing roller facing the secondary transfer roller with the intermediate transfer belt interposed therebetween.

By the way, in the case of a configuration in which the secondary transfer is performed by applying a voltage having a polarity opposite to the normal charge polarity of the toner to the secondary transfer roller, the transfer performance deteriorates when handling a low resistance recording material such as a vapor-deposited paper. I have something to do. This is because a part of the current supplied to the secondary transfer roller passes through the non-transfer surface of the recording material (the back surface of the transfer surface on which the toner image is transferred) and leaks to other transfer rollers, etc., and the toner is static. This is because the effective current that contributes to the formation of the electrically urging transfer electric field is reduced.

On the other hand, Patent Document 1 describes a configuration in which a secondary transfer roller is connected to a ground potential and a voltage having the same polarity as the normal charging polarity of the toner is applied to the opposing roller to perform secondary transfer. In this configuration, most of the current supplied to the opposing roller reaches the transfer surface of the recording material, which contributes to the formation of a transfer electric field between the intermediate transfer belt and the recording material, resulting in low resistance recording. Stable transfer performance can be expected even when handling materials.

Japanese Unexamined Patent Publication No. 2004-184875

The high-voltage substrate that applies a voltage to the opposing roller located inside the intermediate transfer belt is often arranged inside the intermediate transfer belt. However, if the capacity of the high-voltage substrate is increased due to the productivity improvement of the image forming apparatus, or if a cooling fan for the resistor attached to the high-voltage substrate is required, a space for arranging the high-voltage substrate inside the intermediate transfer belt is secured. It can be difficult.

Therefore, an object of the present invention is to provide an image forming apparatus capable of obtaining stable transfer performance without providing a large arrangement space for a high-voltage substrate inside the intermediate transfer belt.

In one aspect of the present invention, an image forming portion for forming a toner image, an intermediate transfer belt on which the toner image formed by the image forming portion is transferred, and an intermediate transfer belt arranged in contact with the inner surface of the intermediate transfer belt are arranged. It has one roller and is arranged so as to be in contact with the outer surface of the intermediate transfer belt and the first unit which can be pulled out from the apparatus main body of the image forming apparatus, and forms a transfer nip between the first roller. It has a second roller and a high-voltage substrate that applies a voltage having the same polarity as the normal charging polarity of the toner image to the first roller in order to transfer the toner image from the intermediate transfer belt to the recording material. In a state where the second unit that can be pulled out from the toner and the second unit are mounted at a predetermined mounting position of the apparatus main body, the high voltage substrate and the first roller are electrically connected, and the second unit is formed. The image forming apparatus is characterized by comprising an electrical contact portion configured to disconnect the high-voltage substrate and the first roller in a state of being pulled out from the mounting position.

According to the present invention, stable transfer performance can be obtained without providing a large arrangement space for a high-voltage substrate inside the intermediate transfer belt.

The schematic diagram of the image forming apparatus which concerns on embodiment. The schematic diagram which shows the periphery of the secondary transfer part of the image forming apparatus which concerns on embodiment. The figure (a, b) for demonstrating attachment / detachment of the transport unit which concerns on embodiment. The schematic diagram (a, b) which shows the internal structure of the transport unit which concerns on Example 1. FIG. The schematic diagram (a, b) which shows the connection structure of the secondary transfer unit and the intermediate transfer belt which concerns on Example 1. FIG. The schematic diagram for demonstrating the support structure and the power supply structure of the opposed roller which concerns on Example 1. FIG. The schematic diagram (a, b) for explaining the image forming apparatus which concerns on Example 2. FIG.

Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing the configuration of an image forming apparatus 100 according to one of the embodiments. The image forming apparatus 100 includes a tandem type intermediate transfer type image forming engine in which four image forming portions 1Y, 1M, 1C, and 1K are arranged in series along the horizontal portion of the intermediate transfer belt 31 in the apparatus main body 110. It is an electronic photo printer installed in. The image forming apparatus 100 forms an image on the sheet material S according to the image information transmitted from, for example, an external device. The sheet material S used as the recording material includes paper such as plain paper and cardboard, surface-treated sheets such as plastic film, cloth, and coated paper, and specially shaped sheet materials such as envelopes and index paper. Various sheets of different sizes and materials can be used. Further, the "image forming apparatus" includes a copying machine, a multifunction device, a commercial printing machine, and the like, in addition to a printer having only a printing function.

Each image forming unit 1Y to 1K has a photosensitive drum 11 which is a drum-shaped electrophotographic photosensitive member, a charger 12, an exposure device 13, a developer 14, and a drum cleaner 15. When the image information and the execution instruction of the image forming operation are input to the image forming apparatus 100, the surface of the photosensitive drum 11 on which the charging device 12 rotates is uniformly charged. The exposure apparatus 13 exposes the photosensitive drum 11 based on the image information, and forms an electrostatic latent image corresponding to a monochromatic image of yellow, magenta, cyan, and black on the surface of the photosensitive drum 11. The developer 14 supplies toner charged to a predetermined normal charging polarity to the photosensitive drum 11, and develops an electrostatic latent image into a toner image of each color of yellow, magenta, cyan, and black.

The intermediate transfer belt 31 is stretched on a drive roller 33, a tension roller 34, an opposed roller 32 (also referred to as a secondary transfer inner roller), etc., and is driven by the drive roller 33 to rotate in the clockwise direction in the drawing. Inside the intermediate transfer belt 31, a primary transfer roller 35 is arranged at a position facing the photosensitive drum 11 of each image forming portion 1Y to 1K with the intermediate transfer belt 31 interposed therebetween.

The above toner image creation process in the image forming units 1Y to 1K proceeds in parallel, and the toner of each color is applied by the primary transfer roller 35 to which a bias voltage (primary transfer voltage) opposite to the normal charging polarity of the toner is applied. The image is first transferred to the intermediate transfer belt 31. At this time, the toner images of each color overlap each other, so that a full-color toner image is formed on the intermediate transfer belt 31. Adhesions such as transfer residual toner remaining on the photosensitive drum 11 without being transferred to the intermediate transfer belt 31 are removed by the drum cleaner 15.

The full-color toner image formed on the intermediate transfer belt 31 is conveyed toward the secondary transfer portion by the rotation of the intermediate transfer belt 31. The secondary transfer portion is a nip portion (transfer nip) formed between the opposed roller 32 and the secondary transfer roller 41 facing the opposed roller 32 with the intermediate transfer belt 31 interposed therebetween. The opposing roller 32 functions as the first roller of the present embodiment capable of contacting the inner surface of the intermediate transfer belt 31. The secondary transfer roller 41 functions as a second roller of the present embodiment capable of contacting the outer surface of the intermediate transfer belt 31.

In parallel with the operation of the image forming portions 1Y to 1K and the intermediate transfer belt 31, the sheet material S is fed one by one from the feeding cassettes 61, 62, 63 toward the secondary transfer portion. That is, when any of the feeding rollers 64, 64, 65 corresponding to the feeding cassettes 61, 62, 63 rotates, the sheet material S stored in the feeding cassettes 61, 62, 63 is fed. It is sent to pass 67. When the sheet material S reaches the registration roller 21 via the feed path 67, the registration roller 21 sets the sheet material S at the timing when the toner image supported on the intermediate transfer belt 31 reaches the secondary transfer portion. Send to the secondary transfer section.

In the secondary transfer section, a bias electric field (transfer electric field) is formed between the intermediate transfer belt 31 and the sheet material S by the secondary transfer voltage described later, and in the secondary transfer section, the sheet material is formed from the intermediate transfer belt 31. The toner image is secondarily transferred to S. Adhesions such as transfer residual toner remaining on the intermediate transfer belt 31 without being transferred to the sheet material S are removed by the belt cleaner 36.

The sheet material S that has passed through the secondary transfer unit is conveyed toward the fixing device 5 via the transfer belt 71. The fixing device 5 of the present embodiment is a heat fixing type, and has a rotating body pair made of a roller or a belt and a heating means such as a halogen lamp or a ceramic heater. The fixing device 5 performs a fixing process of fixing the toner image to the sheet material S by applying heat and pressure to the toner image on the sheet material S while sandwiching and transporting the sheet material S between the pairs of rotating bodies. The sheet material S that has passed through the fixing device 5 is discharged to a discharge tray 69 provided outside the image forming device 100 via the discharge path 68. When an image is formed on both sides of the sheet material S, the sheet material S image-formed on the first surface is conveyed again toward the registration roller 21 via the inversion pass 70 and the double-sided pass 72. Then, after an image is formed on the second surface while passing through the secondary transfer unit and the fixing device 5, the sheet material S is discharged to the discharge tray 69.

[Secondary transfer unit]
The secondary transfer unit of the image forming apparatus 100 will be described with reference to FIG. In the present embodiment, a guide roller 37 in contact with the inner surface of the intermediate transfer belt 31 is provided on the upstream side of the opposing roller 32 in the rotation direction R1 of the intermediate transfer belt 31. Therefore, the intermediate transfer belt 31 moves toward the secondary transfer portion along the tension line T which is the circumscribed line of the guide roller 37 and the facing roller 32.

Further, the secondary transfer roller 41 is urged in a direction approaching the opposing roller 32 by the secondary transfer roller spring 42 as an urging member. Therefore, the secondary transfer portion is formed as a nip portion between the secondary transfer roller 41 and the facing roller 32 that are in contact with each other with the intermediate transfer belt 31 sandwiched by a predetermined pressure.

Here, a voltage (secondary transfer voltage) having the same polarity as the normal charging polarity (here, negative electrode property) of the toner used by the image forming portions 1Y to 1K to create the toner image is applied to the facing roller 32. .. On the other hand, the secondary transfer roller 41 is connected to the ground potential via, for example, a metal frame of the image forming apparatus 100. Therefore, a transfer electric field is formed in the secondary transfer unit to electrostatically urge the charged toner particles toward the secondary transfer roller 41 side. When the sheet material S sent out from the registration roller 21 is guided by the pre-transfer guides 43a and 43b and reaches the secondary transfer unit, the toner particles are transferred from the intermediate transfer belt 31 to the sheet material S according to the above transfer electric field. , The toner image is transferred.

By applying a voltage having the same polarity as the toner to the opposing roller 32 inside the intermediate transfer belt 31 as described above, the current supplied to the opposing roller 32 is transferred between the intermediate transfer belt 31 and the sheet material S. It reaches the transfer surface of the sheet material S while forming an electric field. A part of the current that has reached the transfer surface of the sheet material S flows from the transfer surface of the sheet material S to the non-transfer surface, and flows to the grounded secondary transfer roller 41. The other part of the current that has reached the transfer surface of the sheet material S flows through the transfer surface of the sheet material S to a member other than the secondary transfer roller 41 (for example, the pre-transfer guide 43a).

Since the magnitude of the current leaking through the transfer surface of the sheet material S without flowing to the secondary transfer roller 41 depends on the resistance of the sheet material S (particularly the surface resistance), it is a low resistance sheet such as a vapor-deposited paper. The leakage current is larger in the material S. However, regardless of the magnitude of such leakage current, the current supplied to the opposed roller 32 reaches at least the transfer surface of the sheet material S while forming a transfer electric field, so that a stable transfer electric field is formed and transfer is performed. Contributes to improving the stability of performance.

The image forming apparatus 100 of the present embodiment is an apparatus that realizes high productivity, the intermediate transfer belt 31 is conveyed at a speed (peripheral speed) of 400 [mm / s], and the toner is charged to a negative polarity. .. In order to secure the transfer performance even at this speed, for example, a voltage of −10 [kV] is applied to the facing roller 32. However, the speed of the intermediate transfer belt 31 (process speed of image forming operation), the normal charging polarity of the toner, and the values of the secondary transfer voltage are not limited to these.

In order to apply the secondary transfer voltage to the opposed roller 32, a high voltage substrate that generates a high voltage is required. The high-voltage substrate refers to a substrate having a circuit that generates a voltage larger than a commercial power source (voltage supplied to the image forming apparatus 100 from the outside) to which the image forming apparatus 100 is connected. Since the opposed roller 32 is located inside the intermediate transfer belt 31, it is conceivable that the high voltage substrate for the secondary transfer voltage is also arranged in the space inside the intermediate transfer belt 31. However, as a result of the examination, it was difficult to arrange the high-voltage substrate having a high capacity of -10 [kV] inside the intermediate transfer belt 31 because of its relatively large size. For example, in order to arrange the high-voltage substrate inside the intermediate transfer belt 31, it becomes necessary to increase the peripheral length of the intermediate transfer belt 31 or change the tension path of the intermediate transfer belt 31, and the image forming apparatus 100 There was a possibility that it would become large.

In addition, since a high-voltage substrate with a high capacity generates a large amount of heat, it is necessary to pay attention to the cooling performance of the high-voltage substrate. For example, it is conceivable to secure a space for cooling air to flow around the high-voltage substrate, or to arrange a fan for cooling the resistor which is the main heat source. Such a configuration also leads to an increase in the size of the image forming apparatus 100.

Therefore, as will be described in each embodiment described later, in this embodiment, the configuration in which the high-voltage substrate is arranged in the space outside the intermediate transfer belt 31 works. The "space inside the intermediate transfer belt 31" is a space surrounded by the intermediate transfer belt 31 when viewed in the main scanning direction (the axial direction of the opposing roller 32 and the secondary transfer roller 41) at the time of image formation. Refers to the space inside the maximum width of the intermediate transfer belt 31 with respect to the main scanning direction. Further, the "space outside the intermediate transfer belt 31" refers to a space excluding the space inside the intermediate transfer belt 31 in the image forming apparatus 100.

[Transfer unit attachment / detachment configuration]
The attachment / detachment configuration of the transport unit of the image forming apparatus according to the present embodiment will be described with reference to FIGS. 3A and 3B. The image forming apparatus 100 needs to access the transport path of the sheet material S when the sheet material S is clogged in the apparatus or when regular maintenance is performed. As shown in FIGS. 3A and 3B, the image forming apparatus 100 of the present embodiment has a transport unit 8 as a drawing unit that can be drawn out and inserted into the apparatus main body 110 (housing) of the image forming apparatus. By pulling out the transport unit 8, it is possible to access the transport route. Hereinafter, the direction in which the transport unit 8 is pulled out from the apparatus main body 110 is referred to as the front side (front side) of the image forming apparatus 100, and the opposite side thereof is referred to as the rear side (rear side) of the image forming apparatus 100.

In the used state in which the image forming apparatus 100 can execute the image forming operation, the transport unit 8 is attached to a predetermined attachment position in the apparatus main body 110, and the lock handle 81 is in a predetermined lock position (FIG. 3A). The drawer of the transport unit 8 is in a restricted mounting state. In addition, the front door 101 is also closed in the used state.

When the front door 101 is opened, the lock handle 81 can be accessed. When the lock handle 81 is rotated 90 degrees, the transfer unit 8 is unlocked, and the transfer unit 8 can be pulled out as shown in FIG. 3 (b). As a result, at least a part of the transfer member and the guide member constituting the transfer path in which the sheet material S is conveyed in the image forming apparatus 100, such as the secondary transfer roller 41, is exposed to the outside of the apparatus main body 110. That is, the user or the person in charge of maintenance can access the transport path of the sheet material S and perform the work by setting the transport unit 8 in the drawer state shown in FIG. 3 (b).

To return the transport unit 8 to the mounted state, push the transport unit 8 toward the back side of the apparatus main body 110 to the mounted position from the state shown in FIG. 3B, and then push the lock handle 81 90 degrees in the opposite direction. Just rotate and lock.

The first embodiment (Example 1) of the secondary transfer voltage feeding configuration in the present embodiment will be described. 4 (a) is a schematic view of the transport unit 8 of this embodiment as viewed from above, and FIG. 4 (b) is a perspective of the secondary transfer unit 4 and the pre-fixation transport unit 7 in FIG. 4 (a). It is a figure.

As shown in FIG. 4A, the transfer unit 8 includes a registration unit 2 having a registration roller 21, a secondary transfer unit 4 having a secondary transfer roller 41, and a pre-fixing transfer unit 7 having a transfer belt 71. The fixing device 5 is arranged. These elements are attached to the bottom plate 85a constituting the bottom of the frame of the transport unit 8. Further, the transport unit 8 is pulled out toward one side (arrow F) in the main scanning direction at the time of image formation, and is inserted toward the other side (arrow R) in the main scanning direction.

Further, as shown in FIG. 4B, a high voltage substrate 82 for generating a secondary transfer voltage to be applied to the facing roller 32 is attached to the bottom plate 85a. The high-voltage substrate 82 is arranged below the secondary transfer unit 4 and the pre-fixing transfer unit 7, and can be accessed by removing the secondary transfer unit 4 and the pre-fixing transfer unit 7 with the transfer unit 8 taken out. be.

In this embodiment, the high-voltage substrate 82 outputs a high-voltage bias of -10 [kV]. Therefore, when a resistor is placed on the high-voltage substrate 82, the heat generated by the resistor damages other circuit elements on the high-voltage substrate 82. there's a possibility that. Therefore, the resistor 83 arranged apart from the high-voltage substrate 82 is attached to the front plate 85b of the transport unit 8 and is made conductive with the high-voltage substrate 82 by a bundled wire. Further, in order to prevent the resistor 83 itself from being damaged by heat generation, a fan 84 for cooling the resistor 83 is arranged on the front plate 85b.

The power supply that supplies electric power to the high-voltage board 82 is arranged in the main body of the apparatus, and when the transfer unit 8 is mounted, the power supply and the high-voltage board 82 arranged in the transfer unit 8 are electrically conductive via the drawer connector. It is configured to do. When the transport unit 8 is pulled out from the main body of the apparatus, the drawer connector is disconnected and the electrical conduction between the high-voltage board 82 and the power supply is cut off, so that the power supply to the high-voltage board 82 can be stopped more reliably.

The combination of elements arranged in the transport unit 8 is not limited to the one shown in the figure, and for example, the fixing device 5 may be configured to be attached to the main body of the device. In this case, the image forming apparatus 100 has a first main body frame in which a unit for performing a process up to the secondary transfer step for the sheet material S in the image forming operation is arranged, and a second main body in which the unit for performing the steps after the fixing step is arranged. It may be composed of two main body frames, a frame and. Then, the high-voltage substrate 82 may be arranged together with the secondary transfer unit 4 and the registration unit 2 in the transport unit that can be pulled out from the first main body frame.

As described above, in the present embodiment, the high voltage substrate 82 is arranged on the transport unit 8 that can be pulled out from the main body of the apparatus. On the other hand, the facing roller 32 to which the high voltage substrate 82 applies the secondary transfer voltage is arranged in the main body of the apparatus. Therefore, in this embodiment, when the transport unit 8 is changed from the drawer state to the mounted state, the secondary transfer unit 4 is positioned with respect to the intermediate transfer belt unit including the intermediate transfer belt 31, and at the same time, the high voltage substrate 82 and the facing roller are positioned. The structure in which 32 is electrically conducted is adopted. The intermediate transfer belt unit is the first unit of the present embodiment, and the transfer unit 8 is the second unit of the present embodiment, both of which are configured to be retractable with respect to the main body of the apparatus.

[Connection configuration of secondary transfer unit and intermediate transfer belt unit]
First, the connection configuration of the secondary transfer unit 4 and the intermediate transfer belt unit 6 will be described with reference to FIGS. 5 (a and 5). FIG. 5A shows a state in which the transport unit 8 is pulled out from the mounting position of the apparatus main body (a state in which the positioning of the secondary transfer unit 4 is released).

The secondary transfer unit 4 includes positioning pins 47a and 47b and a first contact plate 45 as a conduction member, and these positioning pins 47a and 47b and the first contact plate 45 form a frame of the secondary transfer unit 4. It is attached to the secondary transfer frame 44, which is a body. A first high-voltage bundled wire 46 that conducts with the high-voltage substrate 82 is connected to the first contact plate 45, and the first high-voltage bundled wire 46 is supported by the secondary transfer frame 44.

As shown in FIGS. 5A and 5B, a secondary transfer unit holding member 38 is attached to an intermediate transfer frame 39a provided so as to be retractable with respect to the main body of the apparatus. The intermediate transfer frame 39a is a frame (frame of the intermediate transfer belt unit 6) that rotatably supports a plurality of tension rollers (drive roller 33, tension roller 34, and opposed roller 32 in FIG. 1) for tensioning the intermediate transfer belt 31. Body). A second contact plate 382 is attached to the secondary transfer unit holding member 38. Further, the first contact pin 381 is held by the secondary transfer unit holding member 38 so as to be movable in the axial direction. A first pressing spring (not shown) is arranged between the second contact plate 382 and the first contact pin 381, and the second contact plate 382 and the first contact pin 381 are electrically conductive via the first pressing spring. Has been done. The intermediate transfer belt unit 6 can be pulled out and mounted together with the transport unit 8 in a direction substantially equal to the pull-out direction (arrow F) and the mounting direction (arrow R) of the transport unit 8.

FIG. 5A shows a detached state in which the transport unit 8 is pulled out from the mounting position of the device main body, and FIG. 5B shows a mounted state in which the transport unit 8 is mounted on the device main body. .. Each is a view of the periphery of the secondary transfer unit holding member 38 from the back side and the lower side in the mounting direction (arrow R) of the transport unit 8 with respect to the apparatus main body.

In the mounted state, the two positioning pins 47a and 47b of the secondary transfer unit 4 are inserted into the positioning holes 38a and the rotation stop holes 38b provided in the secondary transfer unit holding member 38, respectively. As a result, the secondary transfer unit 4 is positioned with respect to the intermediate transfer belt unit 6 with respect to the direction intersecting the attachment / detachment direction (arrows F and R) of the transfer unit 8. Further, the first contact pin 381 pressed in the direction of arrow F by the pressing spring comes into contact with the first contact plate 45 (FIG. 5 (b)), so that the high voltage substrate 82 for secondary transfer and the second contact are contacted. The plate 382 is electrically conductive. That is, the first contact pin 381 as the first contact member and the first contact plate 45 as the second contact member electrically connect the high voltage substrate 82 and the facing roller 32 according to the attachment / detachment of the transfer unit 8. The electrical contact portion of this embodiment for disconnecting is configured.

[Support configuration and power supply configuration of facing rollers]
The support configuration of the opposed rollers 32 and the power supply configuration of the secondary transfer voltage inside the intermediate transfer belt unit 6 will be described with reference to FIG. The shaft portion of the opposed roller 32 is rotatably supported at both ends in the axial direction by two bearings 322a and 322b. The two bearings 322a and 322b are in contact with the steps 320a and 320b provided on the shaft portion of the facing roller 32, respectively, and are restricted from moving inward in the axial direction with respect to the facing roller 32. .. The bearings 322a and 322b are not limited to the ball bearings shown in the drawings, and may be, for example, cylindrical roller bearings or slide bearings.

Further, the bearings 322a and 322b are supported by the opposing roller holding members 321a and 321b as holding members. The facing roller holding members 321a and 321b are provided as a part of the frame body of the apparatus main body, or are fixed to the frame body. Then, the opposing roller holding member 321b on one side in the axial direction (arrow F, the opposite side of the second contact plate 382) is fixed to, for example, the frame of the intermediate transfer belt unit 6. As a result, the movement of the facing roller 32, the bearings 322a, 322b and the facing roller holding member 321a on the other side to one side in the axial direction is restricted.

A power feeding unit 40 is provided on the other side (arrow R) in the axial direction with respect to the facing roller 32. The power supply unit 40 is composed of a power supply member 323, a second pressing spring 324, a second contact pin 325, and a power supply cover 326. The feeding member 323, the second pressing spring 324, and the second contact pin 325 are all made of a conductive material and are arranged inside the feeding cover 326.

The feeding member 323 is in contact with the shaft portion of the facing roller 32. The second contact pin 325 is supported by the feeding cover 326 so as to be slidably movable in the axial direction of the facing roller 32, and is axially projectable from the opening of the feeding cover 326. The second pressing spring 324 is arranged between the feeding member 323 in the axial direction and the second contact pin 325, and the feeding member 323 is attached to one side in the axial direction and the second contact pin 325 is attached to the other side in the axial direction. It is gaining momentum.

The power supply cover 326 is attached to the facing roller holding member 321a. Here, a part of the power feeding cover 326 attached to the opposed roller holding member 321a abuts on the surface of the bearing 322a on the side opposite to the surface abutting on the step 320a. Therefore, the bearing 322a is restricted from moving outward (arrow R) in the axial direction with respect to the facing roller 32.

Inside the feeding unit 40, the feeding member 323 is pressed against one end of the facing roller 32 in the axial direction by the elastic force of the second pressing spring 324, and the second contact pin 325 is further pressed against the second contact plate 382. It is pressed against it. As a result, the second contact plate 382 and the facing roller 32 are electrically conducted via the second contact pin 325, the second pressing spring 324, and the feeding member 323.

As described above, when the transport unit 8 is mounted at a predetermined mounting position in the main body of the apparatus, the high voltage substrate 82 and the second contact plate 382 are electrically conductive. That is, when the transport unit 8 is in the mounted state, the opposed roller 32 is electrically conducted with the high voltage substrate 82 for the secondary transfer voltage.

In this embodiment, the insulator uses PC + ABS resin (polycarbonate and acrylonitrile butadiene styrene alloy) as the material of the power supply cover 326. This is because when the intermediate transfer frame 39a is made of a conductor such as a sheet metal connected to the ground potential, the high voltage current flowing through the feeding member 323, the second pressing spring 324 and the second contact pin 325 leaks. This is to prevent it.

By forming a layer of conductive rubber having a predetermined resistance value on the surface of the opposing roller 32, the secondary transfer current can be stabilized and the opposing roller 32 can be prevented from slipping on the back surface of the intermediate transfer belt 31. It can be realized. However, it may be necessary to replace the facing roller 32 because it becomes difficult to supply a stable secondary transfer current due to wear of the rubber layer and adhesion of toner or toner external agent or the like due to long-term use. ..

In this embodiment, the feeding contact pressure to the facing roller 32 is realized by using the second pressing spring 324 incorporated in the feeding unit 40, and if the feeding unit 40 is separated from the facing roller 32, the second pressing is realized. The pressurization of the spring 324 is released. Therefore, for example, as compared with the case where a leaf spring that is in pressure contact with the shaft portion of the facing roller 32 from the outside in the radial direction is used as the feeding member and urging member, the feeding member and the urging member are plastically deformed when the facing roller 32 is replaced. Can be reduced.

As a specific procedure for replacing the opposed roller 32, first, the secondary transfer unit holding member 38 that supports the second contact plate 382 is removed from the intermediate transfer frame 39a, and the intermediate transfer belt 31 is removed. Then, for example, the power supply cover 326 fastened to the facing roller holding member 321a with a screw is removed from the facing roller holding member 321a. As a result, the facing roller 32 can move together with the bearings 322a and 322b in the axial direction (arrow R), so that the facing roller 32 can be removed from the facing roller holding members 321a and 321b.

When mounting a new facing roller 32, the above procedure is reversed, and the facing roller 32 is inserted together with the bearing 322a toward the other side in the axial direction (arrow F) so that the facing roller 32 is inserted into the facing roller holding members 321a and 321b. To hold. Then, by fixing the power supply cover 326 to the facing roller holding member 321a, the mounting of the facing roller 32 is completed.

(Modification example)
The attachment / detachment configuration of the roller member described above with reference to FIG. 6 is applied to the roller member involved in the transfer of the toner image in the image forming apparatus other than the opposed roller 32 (roller in the secondary transfer) arranged inside the intermediate transfer belt 31. Is also applicable. For example, a primary transfer roller 35 (FIG. 1) that transfers a toner image from a photoconductor to an intermediate transfer belt 31 by applying a primary transfer voltage can be mentioned.

Further, in a configuration in which a voltage having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 41, the power feeding unit 40 may be provided on the secondary transfer roller 41 and the detachable configuration described in the implementation may be applied. Further, in the direct transfer method of transferring the toner image from the photoconductor to the recording material without using the intermediate transfer body, the detachable configuration described in Example 1 may be applied to the transfer roller in contact with the photoconductor.

In the first embodiment, the configuration for electrically conducting the high voltage substrate 82 and the facing roller 32 via the secondary transfer unit 4 has been described, but the high voltage board 82 of the transport unit 8 and the facing roller 32 of the apparatus main body are more directly connected. It is also possible to make it conductive. Hereinafter, as the second embodiment, a mode in which the connection configuration of the high voltage substrate 82 and the facing roller 32 is different from that of the first embodiment will be described. In the following description, it is assumed that the elements having the same reference numerals as those of the first embodiment have substantially the same configuration and operation as those of the first embodiment, and the elements different from those of the first embodiment will be mainly described.

FIG. 7A shows a state in which the intermediate transfer belt unit 6 and the transfer unit 8 are viewed from above in a state where the transfer unit 8 is pulled out. FIG. 7B shows a state in which the intermediate transfer belt unit 6 and the transfer unit 8 are viewed from above in a state where the transfer unit 8 is inserted to the mounting position.

As described above, the intermediate transfer belt 31 is stretched on a plurality of tension rollers including the opposing rollers 32, and each roller is supported by the intermediate transfer frames 39a and 39b provided in the main body of the apparatus. A feeding unit 40 similar to that of the first embodiment is attached to the opposed roller 32, and a third contact pin 327 corresponding to the second contact pin 325 (FIG. 6) of the first embodiment is projected from the intermediate transfer frame 39b. 7 (a). However, unlike the first embodiment, the power feeding unit 40 is provided on the upstream side (arrow F) in the mounting direction of the transport unit 8, and the third contact pin 327 projects in the direction of the arrow F. Further, the third contact pin 327 is slidable along the mounting direction of the transport unit 8, and is attached in the direction of the arrow F by the third pressing spring corresponding to the second pressing spring 324 (FIG. 6) of the first embodiment. It is being pushed.

On the other hand, in the transport unit 8, the high-voltage substrate 82 arranged on the bottom plate 85a and the third contact plate 86 arranged on the front plate 85b are connected by a second high-voltage bundle wire 87. The third contact plate 86 is arranged at a position facing the third contact pin 327 in the mounting direction of the transport unit 8.

As described above, the intermediate transfer frame 39 is positioned with respect to the frame body of the apparatus main body, and the transfer unit 8 in the drawn state (FIG. 7A) is inserted in the direction of the arrow R to be in the mounted state ( FIG. 7 (b)). At this time, the third contact plate 86 comes into contact with the third contact pin 327 urged by the third pressing spring, so that the high voltage is passed through the second high voltage bundle wire 87, the third contact plate 86, and the power feeding unit 40. The substrate 82 and the facing roller 32 are electrically conductive. That is, the third contact pin 327 as the third contact member and the third contact plate 86 as the fourth contact member electrically connect the high voltage substrate 82 and the facing roller 32 according to the attachment and detachment of the transfer unit 8. The electrical contact portion of this embodiment for disconnecting is configured.

(Other embodiments)
Although the exemplary embodiments have been described above with reference to the drawings, the present invention should not be construed as being limited to the exemplified embodiments. That is, the invention described in the claims should be most broadly interpreted as including all the modifications of the illustrated embodiments and the uniform structure and function.

1Y, 1M, 1C, 1K ... Image forming unit / 4 ... Secondary transfer unit / 6 ... First unit (intermediate transfer belt unit) / 8 ... Second unit (conveyance unit) / 31 ... Intermediate transfer belt / 32 ... First 1 roller, roller member (opposing roller) / 41 ... second roller (secondary transfer roller) / 45 ... electrical contact part, second contact member (first contact plate) / 82 ... high voltage substrate / 83 ... resistor / 84 ... Fan / 86 ... Electrical contact portion, fourth contact member (third contact plate) / 322a, 322b ... Bearing / 323 ... Feeding member / 326 ... Cover / 327 ... Electrical contact portion, third contact member (third contact pin) ) / 381 ... Electrical contact portion, first contact member (first contact pin)

Claims (8)

The image forming part that forms the toner image and
It has an intermediate transfer belt on which the toner image formed by the image forming unit is transferred, and a first roller arranged in contact with the inner surface of the intermediate transfer belt, and can be drawn out from the main body of the image forming apparatus. 1st unit and
A second roller that is arranged so as to be in contact with the outer surface of the intermediate transfer belt and forms a transfer nip between the first roller and the toner image for transferring the toner image from the intermediate transfer belt to the recording material. A second unit that has a high-voltage substrate that applies a voltage having the same polarity as the normal charging polarity to the first roller and can be drawn out from the main body of the apparatus.
In a state where the second unit is mounted in a predetermined mounting position of the apparatus main body, the high voltage board and the first roller are electrically connected, and in a state where the second unit is pulled out from the mounting position. An electrical contact portion configured to disconnect the high-voltage substrate and the first roller,
An image forming apparatus comprising. A secondary transfer unit including the second roller and a frame body that rotatably supports the second roller is arranged in the second unit.
The electric contact portion is provided in the first contact member provided in the first unit and electrically connected to the first roller, and is provided in the frame of the secondary transfer unit to be electrically connected to the high voltage substrate. Includes a second contact member that is connected to and contacts the first contact member with the second unit mounted in the mounting position.
The image forming apparatus according to claim 1. The electric contact portion is provided in a third contact member provided in the first unit and electrically connected to the first roller, and is provided in a frame of the second unit and electrically connected to the high voltage substrate. A fourth contact member that comes into contact with the third contact member while the second unit is mounted at the mounting position.
The image forming apparatus according to claim 1. A resistor arranged at a position separated from the high-voltage substrate in the second unit and electrically conducted with the high-voltage substrate,
A fan arranged in the second unit and cooling the resistor,
Have more,
The image forming apparatus according to any one of claims 1 to 3. The high voltage substrate is attached to the bottom of the second unit and is located below the second roller.
The image forming apparatus according to any one of claims 1 to 4. By pulling out the second unit from the mounting position, the connection between the power supply arranged in the apparatus main body and the high voltage board is released.
The image forming apparatus according to any one of claims 1 to 5. The second unit slides in a direction along the axial direction of the first roller with respect to the apparatus main body.
The image forming apparatus according to any one of claims 1 to 6. The first unit is
A bearing that rotatably supports the first roller,
A holding member that holds the bearing and
It is formed of a feeding member and an insulator that come into contact with one end of the first roller in the axial direction of the first roller and electrically conduct the first roller and the high-voltage substrate to hold the feeding member. Cover and
Have,
With the cover attached to the holding member, the axial movement of the first roller and the bearing is restricted.
With the cover removed from the holding member, the first roller and the bearing can be moved in the axial direction to be removed from the holding member.
The image forming apparatus according to any one of claims 1 to 7.

Images